An example of movement for the player including gravity.

player-movement-gravity-example.lua

function move_player(p)
	local mspd = p.mvspd
	if (btn(0)) then p.dx=-mspd end
	if (btn(1)) then p.dx=mspd end
	 
	-- jump function
	jump(p)
	
	-- process gravity
	p.dy+=gravity
	
	-- apply physics
	p.x += p.dx
	p.y += p.dy
	p.dx = 0	
end